Terry Herbert, from Burntwood, Staffordshire, came across the hoard as he searched a field near his home with his trusty 14-year-old detector.

Experts said the collection of more than 1,500 pieces - which will be officially classified by a coroner as treasure - is unparalleled in size and may have belonged to Saxon royalty. The hoard, believed to date back to the seventh century, contains around 5kg of gold and 2.5kg of silver, far bigger than previous finds - including the Sutton Hoo burial site.

It may take more than a year to value the collection and, given its scale, the financial worth of the hoard cannot be estimated.

Leslie Webster, former keeper at the British Museum's Department of Prehistory and Europe, said: "This is going to alter our perceptions of Anglo-Saxon England as radically, if not more so, as the Sutton Hoo discoveries. (It is) absolutely the equivalent of finding a new Lindisfarne Gospels or Book of Kells."

Many of the items in the hoard are warfare paraphernalia, including sword pommel caps and hilt plates, often inlaid with precious stones. The exact location of the discovery has not been disclosed but it is understood to be near the Lichfield border in South Staffordshire.

Mr Herbert, who has been metal detecting for 18 years, came across the buried hoard in July after asking a farmer friend if he could search on his land. He said: "I have this phrase that I say sometimes; 'spirits of yesteryear take me where the coins appear', but on that day I changed coins to gold. I don't know why I said it that day, but I think somebody was listening and directed me to it.

"Maybe it was meant to be, maybe the gold had my name on it all along, I don't know. My mates at the (metal detecting) club always say if there is a gold coin in a field I will be the one to find it. I dread to think what they'll say when they hear about this." He added: "This is what metal detectorists dream of, finding stuff like this. But the vast amount there is is just unbelievable."

Dr Kevin Leahy, National Finds Adviser from the Portable Antiquities Scheme, catalogued the hoard. He said: "The quantity of gold is amazing but, more importantly, the craftsmanship is consummate. This was the very best that the Anglo-Saxon metalworkers could do, and they were very good."